


You like that Daddy?

by 8Verity8



Category: Merlin (TV), Merlin - Fandom
Genre: Age Difference, Aged-Up Character(s), Aging Spell is physical only, Anal Fingering, Anal Sex, Arthur Knows About Merlin's Magic, Blow Jobs, Bottom Merlin, Coming Untouched, Daddy Kink, De-Aged Merlin, Established Relationship, Gay Sex, I'm Going to Hell, M/M, Magically Aged Down Merlin, Magically Aged Up Arthur, Outdoor Sex, Possessive Arthur, Praise Kink, Rimming, Teasing, Top Arthur Pendragon (Merlin)
Language: English
Status: In-Progress
Published: 2018-07-16
Updated: 2018-07-20
Packaged: 2019-06-11 16:19:21
Rating: Explicit
Warnings: Underage
Chapters: 2
Words: 3,771
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/15319368
Author URL: https://archiveofourown.org/users/8Verity8/pseuds/8Verity8
Summary: Merlin and Arthur are returning from gathering some intel. At Arthur's suggestion Merlin alter's their ages so they can disguise themselves as father and son to blend in. Seeing a larger, more mature looking Arthur is having some unforeseen (and hard!) consequences on the teenage Merlin. Thankfully Arthur seems to be into it as much as he is.





	1. Coming Clean

**Author's Note:**

  * For [A_Diamond](https://archiveofourown.org/users/A_Diamond/gifts).



> I wrote this up rather quickly in response to a casual prompt in a chat thread. It is un-beta'd, all mistakes are mine. 
> 
> I hope you enjoy!
> 
>  
> 
> Note: Arthur is matured physically to about age 35/40, while Merlin is physically de-aged to about 16/17. The spell does not impact their mental ages at all. 
> 
> *If this hits your squick factor, that's cool. Just don't read.
> 
> **Update! I promised to write another chapter if/when this broke 200 kudos, which it has! Thank you all, you are awesome! I plan to start working on a chapter 3 (possibly more) in October as soon as I finish writing the Bang fics I am working on. Thank you all for your patience!

Merlin sighed as he shifted uncomfortably atop his horse. The aging spell Arthur had asked him to perform on them both was having some unforeseen consequences. Initially he had thought Arthur’s idea to age him up had been brilliant—they needed information and it was the perfect disguise. He hadn’t been as keen about the part where he was supposed to regress his own age a few years back though. It was so the two would make a convincing father and son, he had gone along with it because it was a smart plan. 

Unfortunately, that meant that he was now sitting astride a horse, in a horny teenage body, watching Arthur’s shirt stretch tight across his very fit and much broader shoulders under the hot sun. Each time Arthur lifted his shirt to let the air circulate Merlin would catch tantalizing glimpses of skin and the swell of his ass pressed flush to the back of the horse.

Which had led to the currently very big, very hard problem in his pants. A problem which he doubted Arthur would be inclined to take care of until they were safely back in the Citadel and the spell had been lifted from them both. Which was, in Merlin’s opinion, a damn shame because this older version of Arthur was doing things to Merlin. He decided they were definitely going to be exploring that thought further sometime in the near future. But for now, just thinking about it was making Merlin’s very horny, teenage cock spasm in want, pressing it harshly against his rapidly tightening trousers.  
Once again, Merlin shifted, pressing a hand to his cock in a vain attempt to bring himself some relief.

“What are you doing back there, Mer-lin?”

Arthur’s voice interrupted his erotic musings, bringing his head up with a start as he tried to hide both his hard cock and his guilty hand from Arthur’s keen gaze.

“Nothing!” He answered guiltily as Arthur’s eyes bored into him.

“Oh really?” Arthur asked as he turned his horse around and brought it flush with Merlin’s.

“That doesn’t look like nothing to me,” he smirked, his eyes flicking pointedly to Merlin’s crotch, which gave an answering twitch. Damn Arthur and his stupid lips, and his own stupid cock, which definitely seemed to like obeying Arthur more than him. They were going to have words in the near future damn it!

“Oh, I’m sorry Daddy. I just seem to be having some problems with these damn teenage hormones!” Merlin snapped.

Arthur took in a sharp breath, his eyes dilating, as he shifted suddenly on his horse. Merlin looked down in surprise to see Arthur’s cock swelling slightly in his trousers as well. A smile grew on Merlin’s face at the sight.

“Oh, you like that, do you Daddy?” Merlin smirked at Arthur. Noting the way his hands clenched around his horse’s reigns before he turned the horse abruptly and set a brisk pace. Merlin hurried to follow on his horse, wondering if he had upset Arthur after all. 

A few minutes later he noticed with a sense of relief that Arthur was turning off the road up ahead and making his way to a clearing hidden back a ways from the path. There he quickly dismounted and began attending to his horse.

“We’re going to set up camp here,” he told Merlin, his voice hoarse with need. 

“But it’s still early yet,” Merlin protested. “We can still easily make it back to Camelot tonight.”

Suddenly Arthur was towering over Merlin. “Don’t you want to please your Daddy?” he purred.

The sudden desire that ripped through Merlin at those words robbed him of the ability to breathe, let alone speak. He nodded mutely up at Arthur as he tried to catch his breath.

“Good,” Arthur responded, pleased. He lifted a hand to stroke Merlin’s hair. “Set up camp while I take care of the horses; and be quick so Daddy can take care of his little boy.

With that Arthur turned to attend to the horses, while Merlin set the camp up in record time. When he was done he stood awkwardly next to Arthur, waiting for him to tell him what to do next.

“There’s a lake just down the hill there where we can get cleaned up,” Arthur told him. “Come on, Daddy wants to make sure you’re nice and clean.”

“I thought my Daddy wanted me to be a dirty boy though,” Merlin teased.

“Oh, I do,” Arthur agreed. “But I need to get my boy all clean, so Daddy can dirty you up properly.”

He gave Merlin a leering grin as he dragged him down to the water and helped him undress. 

“You’re so much smaller like this,” Arthur observed as his hands trailed over Merlin’s neck and down his chest. He tentatively reached out his fingertips to graze lightly over Merlin’s stiff, but obviously smaller cock, before wrapping his large hand around him, engulfing it within.

“You’re also quite a bit bigger too you know,” Merlin retorted, the observation stinging his modest, yet still present ego. “I’m not that small.”

“No, you’re not, you’re perfect,” Arthur breathed, taking his hand and leading him into the water. The cool water felt refreshing against his skin as his Daddy helped wash the dirt and grime of the road from him. His large hands attentive as they bathed his little boy. Merlin helped to wash his Daddy in turn, marveling at how large Arthur was and what he had to look forward to for years to come.  
His cock, long denied, was heavy and red between his legs as they worked. Twitching in anticipation when Arthur’s hard body pressed against his, as his Daddy’s large hands rubbed down every inch of him. Merlin wasn’t sure how much more of this he could take, but Daddy had promised to take care of him, so all he could do was wait.

Once they were both clean they walked hand in hand back to camp where Arthur—no, his Daddy he reminded himself—lowered him to the bedrolls laying flush together, side-by-side. Daddy then crawled over him, dwarfing Merlin’s smaller body with his own. He blocked out the sun as he took Merlin’s lips in a gentle but deep kiss. In that moment his Daddy became his entire world.  
Merlin drew in a ragged gasp as his Daddy moved to suck at his neck, then his nipples before leaving a hot, wet trail down to his cock. 

“You’re so beautiful baby,” his Daddy marveled, placing a few sweet kisses on Merlin’s dick. He licked teasingly at the slit, sucking the pre-cum up with a moan before swallowing Merlin down. 

Oh god, there were definitely some advantages to being smaller, Merlin thought desperately as he was engulfed by the hot, wet heat of Arthur’s mouth. Arthur’s throat constricted around his cock as he swallowed, turning Merlin into a moaning, writhing mess beneath him. Arthur then lifted up to tongue the head some more, dipping into his slit to lick up more of the pre-cum pooling there before plunging back down again.

He wished he could prolong the moment, but he couldn’t wait any longer. The stimulation was too much. He tried to warn Arthur but his Daddy, sensing he was close, picked up the pace. He sucked frantically on his cock, moaning around him when Merlin canted his hips into the air, trying to drive his dick deeper into Arthur’s hot mouth. Arthur’s hands reached around and grabbed onto his ass, his fingers digging into the flesh as he fucked his face with Merlin’s cock.

Merlin couldn’t take it anymore, he was so close, so close—he was there! The world went white as wave, after wave of pleasure coursed through him. His cock spurting streams of cum down his Daddy’s throat which his Daddy swallowed up greedily.

He came back to himself as his Daddy was sucking and licking his softening cock gently, making sure his baby was completely clean. Merlin gazed down on his Daddy with a lazy, satisfied smile which Arthur returned.

“There. Didn’t I say Daddy would take good care of his baby?”


	2. Getting Dirty

**Summary for the Chapter:**

> Arthur F**cks his baby boy.
> 
> This is nothing but pure, kinky AF SMUT! With maybe a dash of fluff thrown in... maybe. But it's fluff in a sexy, kinky context.

**Notes for the Chapter:**

> Ask and you shall receive!
> 
> This is unbeta'd, and I've been staring at a computer screen for hours. So there probably ARE mistakes and they are ALL mine.
> 
> So, never really thought ANY of these kinks were my thing... that being said, I think maybe I enjoyed writing this a bit too much. You learn new things about yourself every day. :)
> 
> I hope all of you enjoy, and please leave comments! The only reason this chapter exists is because you all made me feel all warm and fuzzy from your wonderful and sweet feedback. Who knows, maybe you will inspire a chapter 3.

Arthur’s stomach clenched with desire as he looked down at Merlin. He watched the sunlight dance across his baby’s pale smooth skin, teasing its way through the leaves above them. Lanky limbs sprawled across their bedrolls with wild abandon, creating one of the most beautiful canvas’s Arthur had ever seen. 

Warring emotions threatened to overwhelm him as Merlin opened his eyes, his gaze adoring and trusting. His unwavering faith in Arthur was humbling—Arthur feared that he wasn’t worthy of Merlin’s admiration—even as he found it intoxicating.

When Merlin looked at him like that he wanted to get down on his knees and worship him, make him understand that he was Arthur’s whole world. The beginning and the end for Arthur. But he also wanted to break him—he wanted to see Merlin come undone—knowing that he alone had the privilege to see this side of Merlin. Only he could mark that perfect skin with bite marks and bruises. Only he could make Merlin cry and beg from his touch alone. 

“Mine,” he whispered, looking down at Merlin possessively. 

Merlin’s eyes shone with unshed tears as he held Arthurs gaze.

“Yes,” he agreed. “I’m yours. Always yours, Arthur.”

Arthur let out a growl, wrenching Merlin onto his knees and into his arms. He needed to hold him, to kiss him—to physically lay his claim on the beautiful boy before him. Merlin was so powerful, Arthur knew he had yet to comprehend how powerful Merlin truly was, and yet he submitted willingly to Arthur’s desires… to his will.

“I need you,” Arthur gasped. “I need—”

“Yes,” Merlin whimpered, his smaller frame shivering against him in anticipation. “Please Daddy, please, I need you too.”

“Get on your hands and knees for Daddy,” Arthur ordered, pulling away as Merlin hurried to obey.

He reached down to palm his aching cock, as Merlin spread his legs wide, displaying his tightly furled hole to Arthur’s gaze. It winked at him, begging for his attention. Arthur took a deep breath to steady himself, he was so tempted to grab that sweet ass and slam his cock deep inside. Take what his baby offered up so sweetly and work that pretty little hole open with his fat cock. 

His painfully hard erection twitched in his hand, making Arthur moan, as he remembered the last time he had worked Merlin open that way. The sexy gasps he had let out while Arthur forcibly stretched his hole. Disappointment filled him briefly as he realized he would have to exercise patience. Merlin could handle taking his cock unprepared just fine, but his little boy couldn’t. As much as Arthur wanted to see his boy wrecked, he wanted him to enjoy every minute of it.

He thanked the gods for the willpower his greater age was currently giving him, as he told his cock to wait just a little while longer. He slowly got to his knees to kneel behind Merlin, letting his dick swing freely as he dragged his hands softly up the back of Merlin’s thighs. It swayed, hard and heavy between his legs when he reached forward to push Merlin’s head to the ground, bobbing gently in anticipation as he leaned back again. He noted with satisfaction that Merlin’s entrance was now more prominently on display than before, and eager for his attention.

Laying on his stomach, he took his baby’s hips in both hands, using his fingers to spread him open as he placed a sloppy kiss over his hole. It puckered underneath his lips as his baby let out a small gasp. Before long he was whimpering and moaning, pushing his ass back on to Arthur’s tongue as he sucked gently at his rim and swirled his tongue teasingly over the twitching hole. Encouraging the tight muscle to relax.

“Come on baby, let Daddy in,” Arthur encouraged before attacking his baby’s entrance again.

He ducked down briefly to lick at Merlin’s swaying balls, sucking them into his mouth and drenching them with spit before licking a hot, wet path back to his hole. He could feel Merlin shiver beneath him as a gentle breeze brushed over the moist skin hanging below. Smiling to himself he let his tongue circle his baby’s hole, tighter and tighter with each pass until, at last, it dipped into the center. He buried his face deeper between the cheeks of his little boys perfectly smooth ass, breathing in his scent, as he kissed his baby in the most intimate place possible. 

“Oh, fuck Daddy—” Merlin whimpered, when Arthur’s tongue finally pushed inside, the entrance relaxing as Merlin’s channels sucked him in. 

He thought about admonishing his baby for using such language, but he would have to stop what he was doing, and neither of them wanted that. Instead he doubled his efforts, sucking his baby’s rim into his mouth and licking his hole into submission. He pulled back to kiss and lick at his entrance again as Merlin pushed his ass into Arthur’s face, chasing after the pleasure his Daddy’s tongue was giving him. 

“Patience baby, Daddy’s got you.” Arthur murmured soothingly, rubbing the small of his back for a moment before ordering him to stay where he was.

“I’ll be right back,” he promised. 

He heard Merlin whimper behind him in surprise. Moving swiftly, he searched the saddle bags for the oil he knew Merlin always kept close by. Bottle in hand he returned to Merlin, placing soft kisses down his back in apology.

“I’m sorry I had to leave you baby,” he murmured between kisses. “Daddy needs to make sure you are nice and ready though baby, I don’t want to hurt you.”

“I can take it Daddy,” Merlin gasped. “I swear, I can—”

“I know baby, I know,” Arthur assured him. “But, I don’t want to hurt you sweetheart. A good Daddy is supposed to take care of his little boy. You trust me take care of you, don’t you baby?” 

“Of course, Daddy!” Merlin gasped, as Arthur trailed a single finger down his crack and circled his hole softly.

“Good, then you need to let Daddy prepare your tight little hole, so it can take Daddy’s cock properly,” he admonished.

“Yes, Daddy,” Merlin whispered, burrowing his face in his arms to hide from his Daddy’s rebuke.

“That’s a good boy,” Arthur praised before opening the bottle in his hand and dripping oil down Merlin’s crack. He pushed Merlin forward slightly, tilting his ass higher into the air so the oil would pool in his relaxed hole instead of dripping on to the ground, while he covered several of his fingers.

Grabbing on to Merlin’s hip with his left hand to anchor him in place, he brought his slicked-up hand to his quivering entrance. By now Merlin’s entire body was shaking with tension, his cock hard and leaking again between his legs.

Arthur toyed with the idea of teasing him further but realized he couldn’t hold on much longer himself. So he pressed a slicked-up finger to Merlin’s entrance, anticipating a little pushback from the muscle before it allowed him entrance. Instead, his finger was sucked right up in to his little boy’s heat, all the way to the first knuckle, ripping a moan from his baby as it slipped inside. He moaned in turn as Merlin’s tight channel clenched tightly around his finger, trying to suck him in deeper. 

Slowly he pulled back, working a second digit in easily beside the first. He scissored his fingers gently, adding more oil until Merlin’s channel was nice and slick. With his left hand he pushed his baby forward and back a few times, until Merlin caught the hint and started fucking himself on his Daddy’s fingers. Working himself open as quickly as he could, so that Daddy could fuck his tight little hole with his big cock.

Arthur’s breath hitched in his throat as he added a third, and then a fourth finger. Pre-cum dribbled from his pulsing cock as he watched his baby’s hole stretch lewdly around his fingers, each time Merlin fucked back on to his hand.

Finally, Arthur couldn’t take it anymore and pulled his hand from Merlin’s hole. His baby let out a whimper when he fucked back and found nothing but empty air, his gaping hole clenching in need and begging to be filled. 

Merlin moaned and whimpered, presenting his hole to his Daddy like a bitch in heat. Arthur took a moment to appreciate the sight of his baby like this, as he reached down to line his cock up with his little boy’s entrance.

“You’re so perfect baby,” he praised. “Such a good little boy for your Daddy.”

Merlin’s back arched slightly beneath him, as he preened from his Daddy’s words. Arthur knew how much he loved Arthur’s recognition, though he would never seek it out willingly. A warmth of affection stole over Arthur as he rubbed the head of his cock over Merlin’s hole.

“Gods, I love you so much,” he gasped, before driving his cock into Merlin.

Even with all the preparation, it was still a tight fit. Arthur had to fight for every inch as he worked his cock into his baby. Rocking gently, he was able to burrow his cock in deeper with each thrust. His little boy whimpered underneath the onslaught, struggling to accommodate his Daddy’s wide girth. Arthur held him in place as he squirmed, pushing on steadily, he knew his baby could take it.

Closing his eyes, he forced his brain to think of something distracting, anything to keep him from losing his head as his baby’s tight heat clenched around his aching cock. Upcoming patrols, training drills, his father’s disapproving glare—that last one should do it—anything to bring him back from the precipice. 

He took a deep, shuddering breath as he bottomed out, willing himself to hold still as Merlin squirmed beneath him, adjusting to the intrusion. Dropping his forehead to Merlin’s shoulder he bit his lip to cut off the groan that fought to escape. Arthur was determined to give his baby all the time he needed.

He could do this damn it! This is what he needed to do in order to be a good Daddy for Merlin, and that’s what he wanted most of all... to make Merlin happy. His baby deserved the best, and damn it, Arthur was going to give it to him. 

He sighed in relief as Merlin finally relaxed beneath him. Air, he hadn’t even realized he was holding in, rushed out of him with a whoosh. A small stab of pain went through him as he kissed his baby’s neck. His tongue darted out experimentally and tasted the tangy copper of blood.

‘His baby was worth it,’ he smiled to himself.

“Da-ddy,” Merlin whined, clenching his ass tightly around Arthur’s cock as he wiggled underneath him suggestively.

Arthur could take a hint. He pulled out slowly, until just the tip was still inside, before slamming his cock back into his baby’s tight heat. The slick passage let him set a brutal pace, as he finally gave in and fucked his precious little boy like he had wanted to do for hours now.

The wait had been worth it, gods he had never felt anything so good! 

Merlin’s moans and whimpers made him preen as his cock fucked his baby’s tight little passage open. He relished the lewd sounds their bodies made as they came together. The squelching sound of his dick pounding into Merlin’s ass and the harsh crack that resounded each time their bodies slammed together, but the best sound of all was Merlin screaming out when his dick found that secret, special place deep inside. 

Arthur twisted his hips, pounding his cock straight into that spot over-and-over again, relishing the incoherent babbling coming from his baby as Merlin lost it. He looked down, moaning himself when he realized he had the perfect view of Merlin’s hard leaking cock from this angle. It was swinging wildly beneath him, red and angry looking. Slapping against his stomach with a loud smack each time Arthur slammed into him. 

Arthur’s breath caught in his throat, as he watched, clenching Merlin’s hips, driving his cock into him—harder, faster—willing that beautiful cock to cum for him. He wanted to see his baby’s creamy cum spurt out all over. He wanted his little boy to make a filthy mess just for Daddy. He knew his baby was close, knew he could do it, just for him…

“That’s it my love, cum for Daddy baby,” Arthur encouraged between breaths. “You can do it baby, you’re such a good boy for me.”

That was all Merlin needed, he wanted to please his Daddy so bad. He cried out, clenching around Arthur as he came, shaking as ripples of pleasure coursed through him. Arthur held Merlin up as he went limp beneath him. Tipping over the edge as watched Merlin’s cum fly through the air, splattering all over his stomach and the ground below, his untouched cock still swinging wildly as Arthur fucked him through his orgasm. 

Arthur held his little boy close as he filled him with cum, moaning as his baby’s ass milked his cock dry.

“Oh gods, that’s it baby. Take all of Daddy’s cum baby. Fuck you’re so perfect, so perfect for Daddy—" 

Arthur continued to moan and shower his baby with praise as his cock spasmed weekly inside Merlin’s ass. He fell to his side slowly as his energy drained out of him, dragging Merlin along with him. Smug satisfaction ripped through him, as his cock slipped out of Merlin and he could see his cum leaking out of his baby’s gaping hole.

‘Mine,’ he thought possessively, pulling Merlin in close.

He wrapped his body around Merlin’s much smaller one protectively, draping a leg over his baby’s hip, and snaking an arm around his waist to pull him in tightly. Burying his face in Merlin’s neck, he inhaled deeply, enjoying his love’s natural scent mixed with the unmistakable smell of sex.

“Did Daddy dirty you up enough baby?” Arthur asked lightly, remembering their banter from earlier with a small smirk.

“Naw,” replied his baby boy cheekily, smiling back at him over his shoulder. “I think my Daddy can get me a lot dirtier than this.”

“Mmmmm,” Arthur agreed, nipping playfully at Merlin’s shoulder. “Daddy is definitely looking forward to trying.”

**Notes for the Chapter:**

> Feel free to come geek out with me on [tumblr](https://8verity8.tumblr.com/)
> 
> Or send me prompts if you like, wishful thinking and a prompt brought this fic to life, so you never know. You could be my next muse.
> 
> Thank you all for reading. I'm going to go wash my brain out with soap now. ;)

**Author's Note:**

> Feel free to come geek out with me on [tumblr](https://8verity8.tumblr.com/)
> 
> No really, I like friends and "wouldn't it be cool/what if" chats about my favorite boys led to this fic to begin with...so who knows, you could be next muse!
> 
> Haters NOT welcome.


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